Horcruxes have their own ways of defending themselves, so it is possible that Nagini was never venomous until after she became a horcrux. It's possible that she is a boa constrictor.—The preceding unsigned comment was added by 98.250.54.87 (talk • contribs).

Nagini is a reticulated python and I'm 100% sure that it looks exactly like one since I work at a reptile shop. Reticulated pythons are the longest in the world and can grow to 35ft. Where in the movie does it ever say Nagini is venomous? She is a large constrictor.

It says in the book that she's venomous - that there's something in her venom that keeps Arthur Weasley's wounds from healing properly. Oh, and for the record, per Harry Potter: A Pop-Up Book, the filmmakers' intention was to model Nagini after a Burmese python, though with some creative license, as Rowling described the snake as being much longer than an actual snake of that type. ProfessorTofty 02:17, January 23, 2012 (UTC)

In the 1st book the snake let loose by harry is described as being a Boa Constrictor and considering the sign identified the species' origin as Brazil, it is implied that it is a Common Boa Constrictor (Boa Constrictor Constrictor).

The snake portrayed in the 1st movie could be either a Burmese Python or African Rock Python, as they look almost identical. Because the sign in the movie says the snake is from Asia we can infer that it is a Burmese Python.I don’t believe Nagini's appearance was ever likened to a particular snake by Rowling, only that it was over 12 feet long. Based on that distinction we can safely presume that she is a type of constrictor, either a boa or python, considering that a King Cobra is the only non-constrictor to average 12 feet or more in length. Though the King Cobra possibility might explain why Nagini might be venomous, there is absolutely no way a cobra could ever swallow even a baby much less a full grown adult human.

In the Goblet of Fire movie Nagini is animated to be a Burmese Python, essentially. In the later movies Nagini is portrayed as being identical to a Reticulated Python.

Given all the information I’ve just given, we are able to come to a few conclusions:

Every snake in both the books and the movies are depicted as constrictors. </li></li></li></li></li></li>

No constrictor is poisonous (in the muggle world at least). </li></li></li></li></li></li>

No Constrictor has fangs (as described by Rowling). </li></li></li></li></li></li>

There are only 3 snakes that could even conceivably come close to growing large enough to eat an adult human: Reticulated Python, Burmese Python, and a Green Anaconda (all three of which are constrictors). There has never been a recorded example of any snake swallowing or even being able to swallow an adult human (Shoulders get in the way) and certainly none of these three could even, hypothetically, attempt to do so at 12 feet in length, as described by Rowling.</li>

Armed with these facts one can only conclude that either Nagini is a unique creation of Rowling's mind not based on any real snake or is one of the aforementioned 3 snakes that has had a permanent engorgement charm cast upon it as well as a spell to augment her with poisonous fangs.

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There is an inherent flaw in all of this arguing; the movie isn't canon, per se, the book is. To conclude that the only snake it could be are these large snakes is very flawed. 1: We are talking about a fictional magical world. Nagini could have been artificially created (as the snake in the second book when Harry and Draco learn about Wizard duels) and 2: she could have been magically altered, either in growth or to have venom and fangs.

In the book, nothing alludes to the two snakes being the same. In the films in the first movie at 00:06:55 the sign does say SE Asia but this doesn't mean much, what does matter is of what the snake said, or rather shook it's head to, and that was Harry's question about him missing his home. It then points to the sign which reads "born in captivity". The clincher for these two snakes not to be same is time frame.

It is most likely that Nagini met Voldemort after his initial downfall. The snake became a horcrux in 1994 after his second downfall, her venom was used to make an elixir for Voldemort. It should also be noted that the snake from Film One is a completely different color and have completely different camouflage spots from Nagini; the spots and color of a snake are like fingerprints, genetically encoded and specific to each snake. The timing is off and it is unlikely that the two are the same.

However, there is a snake that might be directly related to Nagini which makes far more sense. Voldemort employed the Basilisk to guard the chamber of secrets. It is far more likely that Nagini is a daughter of this great snake. Both share very similar descriptions and form. Both in the film and in the books. Green in color, poisonous, pseudo-restrictors.
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It seems unlikley to me that Nagini is based on a real breed of snake. Perhaps the snake depicted in Harry Potter is of Rowling's own creation and/or only exsists in the Wizarding World. We know the snake at the zoo was a constrictor and that Nagini is poisonous (see the above references to Arthur's wounds) as well as the way Nagini lashed out at Snape rather than constricting him. The only venomous snake large enough to be Nagini is a King Cobra which would have a visible hood.
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actually, a King Cobra's hood is quite narrow and streamlined with it's body even when the snake has chosen to "hood up" as we in the snake hobby like to say. If you put an engorgement charm (or two) on the snake, which still can reach around eighteen feet long (around 6 meters for the brits) WITHOUT an engorgement charm, you've got your snake. Although the idea that Nagini isn't based on a real species is probably true. I highly doubt Rowling cared or knew enough about snakes to try to base her on a real snake. A far more likely possibility that has already been posted is the suggestion of a magically altered snake. Rowling may not have known about snakes, but I'll garantee you Voldemort did. It wouldn't suprise me if he took a Reticulated python or an African Rock python (both of which have a reputation among those of us in the snake hobby to have aggression issues along with their massive size. Which is probably one of the reasons that they used a retic in the movie. By the way, Snape's wounds were VERY realistic to what Retic bites look like when inflicted by a snake that size) and then give that already large and agressive snake highly potent venom. Jethro Mortspear (talk) 02:15, January 7, 2014 (UTC)</li></li>